Use of ~1H cross-relaxation nuclear magnetic resonance spectroscopy to probe the changes in bread and its components during aging

摘要

~1H nuclear magnetic cross-relaxation spectroscopy was used to probe the molecular mobility/rigidity in bread and its components during storage. The Z-spectra lineshapes, attributed to the solid-like polymer fractions of the samples, differed for the bread, gelatinized waxy starch (GX), gelatinized wheat starch (GW), heated flour (HF), and heated gluten (HG). Upon storage, no change was observed in the Z-spectrum of the bread sample, while the Z-spectra for GX, GW, and HG increased in the width as half height of the decomposed broad component (increased rigidity). These trends in the Z-spectra detected by NMR were contradictory to the DSC results that showed an increase in amylopectin retrogradation enthalpy for all samples containing starch, including bread. These trends in the Z-spectra detected by NMR were not reflected by the DSC results that showed an increase in amylopectin retrogradation enthalpy for all samples, including bread. The differences in molecular mobility could not be therefore, due to recrystallized amylopectin and may be attributed to the role of gluten and/or redistribution of water in the amorphous regions of the samples.